Is the amperage of a breaker for total amps combined or on each leg?

Answer 1

The breaker will trip at the amperage notated on the breaker. If it's 100A...it will trip at or around 100A. It does not matter if that breaker is physically tied to another 100A breaker.

To understand this, imagine that you remove the mechanical tie from the two-pole breaker. Now you just have two 100A breakers. In actuality, you always had two 100A breakers. The mechanical tie does not change that.

If you then powered two, separate 120 volt devices from the two breakers, each breaker would allow 100 amperes to pass to each of the devices before tripping.

So why are they tied together? That is done when the two-pole breaker is to be used to power a 240 volt circuit. In AC current, electricity flows in both directions. In a 120 volt circuit, it flows "out" toward the device via the hot (generally the black wire) and "back" via the neutral (generally the white wire). Then the cycle reverses. It does this 60 times per second (60Hz). The amperage in the hot and neutral wires are the same (in the perfect world). Only the hot wire is connected to the breaker.

In a 240 volt circuit, there is no neutral wire. You are using two "legs" of 120 volts each that are 180 degrees out of phase with each other. In other words, as leg 1 is flowing "out", leg 2 is flowing "back". Because they are out of phase, the potential difference is twice the voltage of each line or 240 volts. The current flows out and back at the same 60 Hz but this time via the two hot wires (generally black and red). Each of these hot wires are connected to the two terminals of the two-pole breaker.

Due to mechanical tolerances, one breaker will most likely trip before the other. Therefore, if the rated current, (100 amps), is exceeded on either breaker, that breaker will trip and the other breaker will trip via the mechanical tie. This ensures that all power to the outlet is disconnected. If you removed the tie and only one breaker tripped, there would still be 120 volts connected to the outlet.

In summary, each leg of a single, double (2 phase) or triple (3 phase) breaker is capable of allowing the amount of current denoted on the breaker. The connected circuit, regardless of voltage is protected from exceeding that amperage.

Answer 2

It will have 2 50 amp legs for 240V, as each "leg" needs to be equal in a 240 volt circuit. An easy way to think of 240 volt is as 2 110/120 volt lines, you would need a single 50 amp breaker for single phase 110/120.

Answer 3

Answer for USA, Canada and countries running a 60 Hertz supply service.

Combined. A two-pole 100A breaker will draw 50A on each leg. A three-pole 100A breaker will draw 33A on each leg.

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People have funny concepts about electricity , the above is totally false. A two pole 100A breaker will draw 100A on each leg. A three pole 100A breaker will draw 100A on each leg. The number that is marked on every breaker is the amperage that the breaker is designed to trip at. Sheer reason should tell you that if you wanted to protect a 240 volt load at 50 amps you would not install a breaker that has 100 amps marked on it.

Answer 4

The amperage of a breaker is typically for the total amps combined on both legs. Each leg carries a portion of the total load, so the breaker is sized to protect the circuit from an overload on either leg or on both legs simultaneously.